The present invention relates to the area of chemical synthesis. More particularly, this invention relates to photolabile compounds, reagents for preparing the same and methods for their use as photocleavable linkers and protecting groups, particularly in the synthesis of high density molecular arrays on solid supports.
The use of a photolabile molecule as a linker to couple molecules to solid supports and to facilitate the subsequent cleavage reaction has received considerable attention during the last two decades. Photolysis offers a mild method of cleavage which complements traditional acidic or basic cleavage techniques. See, e.g., Lloyd-Williams et al. (1993) Tetrahedron 49:11065–11133. The rapidly growing field of combinatorial organic synthesis (see, e.g., Gallop et al. (1994) J. Med. Chem. 37:1233–1251; and Gordon et al. (1994) J. Med. Chem. 37:1385–1401) involving libraries of peptides and small molecules has markedly renewed interest in the use of photolabile linkers for the release of both ligands and tagging molecules.
A variety of ortho-benzyl compounds as photolabile protecting groups have been used in the course of optimizing the photolithographic synthesis of both peptides (see Fodor et al. (1994) Science 251:767–773) and oligonucleotides (see Pease et al. Proc. Natl. Acad. Sci. USA 91:5022–5026). See PCT patent publication Nos. WO 90/15070, WO 92/10092, and WO 94/10128; see also U.S. patent application Ser. No. 07/971,181, filed 2 Nov. 1992, and Ser. No. 08/310,510, filed Sep. 22, 1994; Holmes et al. (1994) in Peptides: Chemistry, Structure and Biology (Proceedings of the 13th American Peptide Symposium); Hodges et al. Eds.; ESCOM: Leiden; pp. 110–12, each of these references is incorporated herein by reference for all purposes. Examples of these compounds included the 6-nitroveratryl derived protecting groups, which incorporate two additional alkoxy groups into the benzene ring. Introduction of an α-methyl onto the benzylic carbon facilitated the photolytic cleavage with >350 nm UV light and resulted in the formation of a nitroso-ketone.
Photocleavable protecting groups and linkers should be stable to a variety of reagents (e.g., piperidine, TFA, and the like); be rapidly cleaved under mild conditions; and not generate highly reactive byproducts. The present invention provides such protecting groups and methods for their use in synthesizing high density molecular arrays.